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bb629484d9
SMT now could be disabled via "/sys/devices/system/cpu/smt/control". Status is shown in "/sys/devices/system/cpu/smt/active" simply as "0" / "1". If this knob isn't here then fallback to checking topology as before. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lore.kernel.org/lkml/158817741394.748034.9273604089138009552.stgit@buzz Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
53 lines
1.1 KiB
C
53 lines
1.1 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <linux/bitops.h>
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#include "api/fs/fs.h"
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#include "smt.h"
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int smt_on(void)
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{
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static bool cached;
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static int cached_result;
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int cpu;
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int ncpu;
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if (cached)
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return cached_result;
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if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) > 0)
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goto done;
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ncpu = sysconf(_SC_NPROCESSORS_CONF);
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for (cpu = 0; cpu < ncpu; cpu++) {
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unsigned long long siblings;
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char *str;
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size_t strlen;
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char fn[256];
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snprintf(fn, sizeof fn,
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"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
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if (sysfs__read_str(fn, &str, &strlen) < 0) {
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snprintf(fn, sizeof fn,
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"devices/system/cpu/cpu%d/topology/thread_siblings",
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cpu);
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if (sysfs__read_str(fn, &str, &strlen) < 0)
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continue;
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}
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/* Entry is hex, but does not have 0x, so need custom parser */
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siblings = strtoull(str, NULL, 16);
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free(str);
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if (hweight64(siblings) > 1) {
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cached_result = 1;
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cached = true;
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break;
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}
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}
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if (!cached) {
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cached_result = 0;
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done:
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cached = true;
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}
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return cached_result;
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}
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